Monitor NAT network connections

[Rashkae]

I used to use a perl script called conntrack-viewer that generated very
nice reports showing me all the NAT connections.. (Ie, I could see which
computers in my network were making what connections to the Internet).

Alas, this was designed for kernel 2.4, and doesn't seem to work with
Ubuntu Hardy 2.6 kernels.

Can anyone suggest an alternative program to do the same thing? thanks